1. Field of the Invention
The present invention relates to a cylinder number-controlled internal combustion engine in which the operation of one or more of the cylinders can be stopped.
2. Description of the Prior Art
Such internal combustion engines are conventionally known, for example, from Japanese Patent Application Laid-open No. 78709/90.
The above known internal combustion engine is of a construction such that only one or more predetermined particular cylinder(s) can be stopped. If the cylinder-stopped operation has been continued for a long time, the temperature of a peripheral portion within the stopped cylinder (e.g., the temperature of the cylinder wall surface, the top of a cylinder, the wall surface of the combustion chamber, the engine valve or the like) is dropped as compared with a normal fuel burning operation, and/or an unbalance of an oil rise and drop phenomenon in the stopped cylinder, a sticking of the engine valve, a compression leakage and the like may be produced. As a result, when the engine is restored to an all-cylinder-operated state, the engine is required to be operated in an incompletely warmed state in the cylinder which has been stopped theretofore, thereby causing an imbalance with the continuously operated cylinder(s) to bring about an increase in fuel consumption and a deterioration in the nature of the exhaust gas.
Thereupon, a control is also conducted such that the stopped cylinder is restored to an operative state after a lapse of a predetermined time from the start of the stoppage of the cylinder. With such a construction, however, the desired effect of providing a reduction in pumping loss and a reduction in fuel consumption, due to the stoppage of the cylinder, is not completely obtained, and it is necessary to detect that the above-described imbalance phenomenon is being produced due to an irregular switching of the operation and stoppage of the cylinder. Therefore, it is difficult to inhibit the generation of the imbalance.